1. Field of the Invention
The present invention relates to communication apparatus and communication process (protocol), and more particularly to a wireless asynchronous transfer mode communication system for performing wireless communications in an asynchronous transfer mode (ATM) between a base station (access point) connected to a wireless communication network and one or more terminal stations (mobile terminals) present in an area covered by the base station, and a method of controlling broadcast.
2. Description of the Related Art
In recent years, it has been customary to carry out electronic presentations on the terminals of attendees in conference rooms, and distribute file materials as electronic information to meeting attendees via communication links. In such applications, there has been a demand for the simultaneous distribution of data to the terminals via broadcast because it would be time-consuming to transfer the data to each of the terminals individually.
One conventional system proposed to meet such a demand is disclosed in Japanese laid-open patent publication No. 7-107032, for example.
The disclosed system is a wireless communication system for performing broadcast between one or more master stations and a plurality of slave stations. Each of the slave stations is assigned to one or more groups. The master station has a channel switching instruction transmitting means for transmitting a channel switching instruction signal including a group identification number to identify the group of a slave station and indicative of switching to a designated broadcast channel, to all slave stations in a wireless zone. Each of the slave stations has a channel switching means responsive to a channel switching instruction signal including a group identification number representing the group to which the slave station belongs, for switching the communication channel with the master station to the broadcast channel designated by the received channel switching instruction signal, and a channel switching completion signal transmitting means for transmitting a channel switching completion signal to the master station when the process of switching the communication channel as carried out by the channel switching means is completed. The master station also has a broadcast signal transmitting means responsive to a channel switching completion signal from a slave station within the group identified by the group identification number, for transmitting a broadcast signal to all the slave stations in the group using the broadcast channel designated by the channel switching instruction signal. Each of the slave stations further includes a broadcast signal receiving means for receiving the broadcast signal from the master station using the broadcast channel to which the communication channel has switched, after the channel switching completion signal has been transmitted.
In the conventional wireless communication system, the master station transmits a channel switching instruction signal including a group identification number to all slave stations in the wireless zone. Each of the slave stations in the corresponding group switches the communication channel with the master station to the broadcast channel designated by the received channel switching instruction signal. When the process of switching the communication channel is finished, each of the slave stations in the corresponding group transmits a channel switching completion signal to the master station. In response to the channel switching completion signal from the slave station, the master station transmits a broadcast signal to all the slave stations in the group using the broadcast channel designated by the channel switching instruction signal. After having transmitted the channel switching completion signal, each of the slave stations receives the broadcast signal from the master station using the broadcast channel to which the communication channel has switched.
The conventional wireless communication system operates according to such a protocol that a broadcast channel is assigned in advance to single-burst communications and used for broadcast. Since a single burst is used for communications from a base station, it is difficult to perform broadcast that is based on the sharing of a transfer process by all terminals.
It is therefore an object of the present invention to provide a wireless asynchronous transfer mode communication system for performing broadcast between a plurality of mobile terminals present in an area covered by an access point, and a method of controlling broadcast.
According to an aspect of the present invention, there is provided a wireless asynchronous transfer mode communication system, comprising an access point connected to a wireless communication network for performing wireless communications in an asynchronous transfer mode, an ATM switch connected to the access point, at least one mobile terminal present in an area covered by the access point, for performing wireless communications with the access point, the mobile terminal comprising setting means for establishing a broadcast identifier representative of broadcast in the header of each wireless ATM cell for performing broadcast, determining means for determining the broadcast identifier and header information in the header of each received wireless ATM cell, and switching means for switching between acceptance and discarding of each received wireless ATM cell based on the determined result from the determining means, the access point comprising identifying means for identifying a broadcast identifier in the header of a received wireless ATM cell, and returning means for returning the wireless ATM cell if the broadcast identifier is identified by the identifying means, and transmitting the wireless ATM cell to a downstream burst.
The switching means may comprise means for accepting the wireless ATM cell if the broadcast identifier does not indicate broadcast and if the header information agrees with connection information assigned to the mobile terminal itself, and discarding the wireless ATM cell if the header information does not agree with connection information assigned to the mobile terminal itself, and means for discarding the wireless ATM cell if the broadcast identifier indicates broadcast and if the header information agrees with connection information assigned to the mobile terminal itself, and accepting the wireless ATM cell if the header information does not agree with connection information assigned to the mobile terminal itself.
According to another aspect of the present invention, there is provided a wireless asynchronous transfer mode communication system, comprising an access point connected to a wireless communication network for performing wireless communications in an asynchronous transfer mode, an ATM switch connected to the access point, at least one mobile terminal present in an area covered by the access point, for performing wireless communications with the access point, the mobile terminal comprising setting means for establishing a broadcast identifier representative of broadcast in the wireless overhead of each wireless ATM cell, determining means for extracting the broadcast identifier established in the wireless ATM cell when a downstream burst is received, and determining whether the wireless ATM cell is a broadcast wireless ATM cell or not, comparing means for, if the wireless ATM cell is a broadcast wireless ATM cell, extracting header information of the header of the wireless ATM cell and comparing the extracted header information with connection information assigned to the mobile terminal, and selecting means for, if the extracted header information agrees with the connection information, determining that the wireless ATM cell is a wireless ATM cell transmitted as a broadcast wireless ATM cell from the mobile terminal itself, and discarding the wireless ATM cell, and if the extracted header information does not agree with the connection information, determining that the wireless ATM cell is a wireless ATM cell transmitted from another mobile terminal itself, and accepting the wireless ATM cell, the access point comprising monitoring means for determining whether there is a broadcast identifier in the wireless overhead of the wireless ATM cell received from the mobile terminal, extracting means for, if there is a broadcast identifier in the wireless overhead, extracting the broadcast identifier of the received wireless ATM cell and a mobile terminal source identifier received from the mobile terminal, and returning means for, if the received wireless ATM cell is a broadcast wireless ATM cell, returning the received wireless ATM cell in the access point and transmitting the received wireless ATM cell to a downstream burst.
According to still another aspect of the present invention, there is provided a wireless asynchronous transfer mode communication system, comprising an access point connected to a wireless communication network for performing wireless communications in an asynchronous transfer mode, an ATM switch connected to the access point, at least one mobile terminal present in an area covered by the access point, for performing wireless communications with the access point, the mobile terminal comprising setting means for adding an n-bit broadcast identifier and an m-bit source identifier as connection information to the header of a wireless ATM cell for transmitting broadcast information, extracting means for extracting a broadcast identifier and a source identifier from the connection information in the wireless ATM cell when a downstream burst is received, and selecting means for, if the broadcast identifier is effective, the wireless ATM cell is a broadcast wireless ATM cell, and the extracted broadcast identifier agrees with the source identifier of the mobile terminal itself, discarding the wireless ATM cell, and if the extracted broadcast identifier does not agree with the source identifier of the mobile terminal itself, accepting the wireless ATM cell as a broadcast wireless ATM cell, the access point comprising determining means for extracting a broadcast identifier from the connection information in the header of the received wireless ATM cell, and determining whether the received wireless ATM cell is a broadcast wireless ATM cell based on the extracted broadcast identifier, and returning means for, if the received wireless ATM cell is a broadcast wireless ATM cell, returning the received wireless ATM cell in the access point and transmitting the received wireless ATM cell to a downstream burst.
The access point may comprise means for, if the broadcast identifier is effective, the wireless ATM cell received from the mobile terminal is effective as a broadcast wireless ATM cell, the mobile terminal is set to a returning mode, the source identifier is changed to the broadcast identifier when the received wireless ATM cell is returned, and the source identifier of the returned wireless ATM cell agrees with the broadcast identifier of the mobile terminal itself, discarding the wireless ATM cell received from the mobile terminal, and if the source identifier of the returned wireless ATM cell does not agree with the broadcast identifier of the mobile terminal itself, accepting the wireless ATM cell received from the mobile terminal.
According to yet another aspect of the present invention, there is provided a method of controlling broadcast in a wireless communication network for performing wireless communications in a wireless asynchronous transfer mode, the wireless communication network having an access point, an ATM switch connected to the access point, and at least one mobile terminal present in an area covered by the access point, for performing wireless communications with the access point, comprising the steps of establishing, with the mobile terminal, a broadcast identifier representative of broadcast in the header of each wireless ATM cell for performing broadcast, identifying, with the access point, a broadcast identifier in the header of each wireless ATM cell received from the mobile terminal, returning, with the access point, the wireless ATM cell if the broadcast identifier is identified, and transmitting the wireless ATM cell to a downstream burst, determining, with the mobile terminal, the broadcast identifier and header information in the header of each received wireless ATM cell, and switching, with the mobile terminal, between acceptance and discarding of each received wireless ATM cell based on the determined result, the step of switching comprising the steps of accepting the wireless ATM cell if the broadcast identifier does not indicate broadcast and if the header information agrees with connection information assigned to the mobile terminal itself, and discarding the wireless ATM cell if the header information does not agree with connection information assigned to the mobile terminal itself, and discarding the wireless ATM cell if the broadcast identifier indicates broadcast and if the header information agrees with connection information assigned to the mobile terminal itself, and accepting the wireless ATM cell if the header information does not agree with connection information assigned to the mobile terminal itself.
According to yet still another aspect of the present invention, there is provided a method of controlling broadcast in a wireless communication network for performing wireless communications in a wireless asynchronous transfer mode, the wireless communication network having an access point, an ATM switch connected to the access point, and at least one mobile terminal present in an area covered by the access point, for performing wireless communications with the access point, comprising the steps of establishing, with the mobile terminal, a broadcast identifier representative of broadcast in the wireless overhead of each wireless ATM cell, determining, with the access point, whether there is a broadcast identifier in the wireless overhead of the wireless ATM cell received from the mobile terminal, if there is a broadcast identifier in the wireless overhead, extracting, with the access point, the broadcast identifier of the received wireless ATM cell and a mobile terminal source identifier received from the mobile terminal, if the received wireless ATM cell is a broadcast wireless ATM cell, returning, with the access point, the received wireless ATM cell in the access point and transmitting the received wireless ATM cell to a downstream burst, extracting, with the mobile terminal, the broadcast identifier established in the wireless ATM cell when a downstream burst is received, and determining whether the wireless ATM cell is a broadcast wireless ATM cell or not, if the wireless ATM cell is a broadcast wireless ATM cell, extracting, with the mobile terminal, header information of the header of the wireless ATM cell and comparing, with the mobile terminal, the extracted header information with connection information assigned to the mobile terminal, and if the extracted header information agrees with the connection information, determining, with the mobile terminal, that the wireless ATM cell is a wireless ATM cell transmitted as a broadcast wireless ATM cell from the mobile terminal itself, and discarding the wireless ATM cell with the mobile terminal, and if the extracted header information does not agree with the connection information, determining, with the mobile terminal, that the wireless ATM cell is a wireless ATM cell transmitted from another mobile terminal itself, and accepting the wireless ATM cell with the mobile terminal.
According to a further aspect of the present invention, there is provided a method of controlling broadcast in a wireless communication network for performing wireless communications in a wireless asynchronous transfer mode, the wireless communication network having an access point, an ATM switch connected to the access point, and at least one mobile terminal present in an area covered by the access point, for performing wireless communications with the access point, comprising the steps of adding, with the mobile terminal, an n-bit broadcast identifier and an m-bit source identifier as connection information to the header of a wireless ATM cell for transmitting broadcast information, extracting, with the access point, a broadcast identifier from the connection information in the header of the received wireless ATM cell, and determining, the access point, whether the received wireless ATM cell is a broadcast wireless ATM cell based on the extracted broadcast identifier, if the received wireless ATM cell is a broadcast wireless ATM cell, returning, with the access point, the received wireless ATM cell in the access point and transmitting the received wireless ATM cell to a downstream burst, extracting, with the mobile terminal, a broadcast identifier and a source identifier from the connection information in the wireless ATM cell when a downstream burst is received, and if the broadcast identifier is effective, the wireless ATM cell is a broadcast wireless ATM cell, and the extracted broadcast identifier agrees with the source identifier of the mobile terminal itself, discarding the wireless ATM cell with the mobile terminal, and if the extracted broadcast identifier does not agree with the source identifier of the mobile terminal itself, accepting the wireless ATM cell as a broadcast wireless ATM cell with the mobile terminal.
The step of determining, with the access point, whether the received wireless ATM cell is a broadcast wireless ATM cell may comprise the steps of, if the broadcast identifier is effective, the wireless ATM cell received from the mobile terminal is effective as a broadcast wireless ATM cell, the mobile terminal is set to a returning mode, the source identifier is changed to the broadcast identifier when the received wireless ATM cell is returned, and the source identifier of the returned wireless ATM cell agrees with the broadcast identifier of the mobile terminal itself, discarding the wireless ATM cell received from the mobile terminal, and if the source identifier of the returned wireless ATM cell does not agree with the broadcast identifier of the mobile terminal itself, accepting the wireless ATM cell received from the mobile terminal.
The present invention thus provides a wireless asynchronous transfer mode communication system for performing broadcast between a plurality of mobile terminals present in an area covered by an access point, and a method of controlling broadcast.
According to the present invention, the mobile terminal establishes a broadcast identifier in the header of a wireless ATM cell, and the access point identifies the received wireless ATM cell as a broadcast wireless ATM cell for thereby making it possible to return the wireless ATM cell. Even if data is transmitted from the access point to the mobile terminal by broadcast, using a single burst, the mobile terminal which has performed broadcast does no receive data transmitted thereby.
Furthermore, data transmission efficiency is prevented from being lowered even when broadcast is carried out to transmit n copies of a broadcast WATM cell to respective n mobile terminals that are controlled by an access point, using a single burst.
The above and other objects, features, and advantages of the present invention will become apparent from the following description with reference to the accompanying drawings which illustrate examples of the present invention.